Today, the U.S. Food and Drug Administration conditionally approved Varenzin-CA1 (molidustat oral suspension), the first drug for the control of nonregenerative anemia associated with chronic kidney disease (CKD) in cats. Nonregenerative anemia can be a fatal condition because the cat’s bone marrow is not able to produce enough red blood cells to replace the older or damaged red blood cells that are naturally removed from the blood, resulting in the inability for oxygen to be carried from the lungs throughout the body.

CKD is a disease that requires day-to-day management in cats, and nonregenerative anemia is a complication that often contributes to death or euthanasia of affected cats due to poor quality of life. Cats can develop CKD at any age, but it is frequently diagnosed in older cats. It can be triggered by other diseases or malformation of the kidneys, bacterial or viral infections, kidney inflammation and associated damage (glomerulonephritis), cancers, or a build-up of protein in the kidney (amyloidosis). Cats with CKD develop nonregenerative anemia when their kidneys produce less of a hormone called erythropoietin, which helps the bone marrow produce red blood cells. 

The current treatments available for nonregenerative anemia in cats with CKD include blood transfusion, supplemental iron therapy and erythropoietin replacement. However, there are no erythropoietin treatments approved for use in cats. Varenzin-CA1 works by helping to increase production of erythropoietin in the kidney, which in turn stimulates the bone marrow to produce more red blood cells.

“Varenzin-CA1 is the first drug to receive conditional approval for use in cats, providing access to a novel medicine for our feline companions suffering from nonregenerative anemia due to CKD,” said Tracey Forfa, director of the FDA’s Center for Veterinary Medicine. “Additionally, this is the first drug for cats under expanded conditional approval, a pathway to the marketplace that encourages development of innovative treatments and increases the options for treating animals with uncommon conditions, serious or life-threatening diseases, or diseases without existing or adequate therapies.”

Under conditional approval, the FDA has concluded that the drug is safe for its intended purpose and has a reasonable expectation of being effective. This allows cats suffering from the disease to receive the treatment while full effectiveness data is being collected. The initial conditional approval is valid for one year with the potential for four annual renewals. During this time, the animal drug sponsor must demonstrate active progress toward proving substantial evidence of effectiveness for full approval. If a sponsor does not meet the requirements for substantial evidence of effectiveness at the five-years mark, the product can no longer be marketed. 

Expanded conditional approval authority was granted to the FDA in the Animal Drug User Fee Act of 2018 and is intended for drugs that address a serious or life-threatening disease or condition, or an unmet animal or human health need, and for which demonstrating effectiveness would require a complex or particularly difficult study or studies. The expanded conditional approval program will sunset in 2028.

The reasonable expectation of effectiveness of Varenzin-CA1 was evaluated in a study conducted in two phases. The first phase involved a multi-center, double-masked, randomized, placebo-controlled field effectiveness and safety study. The second phase was an unmasked, optional continuation of the field study. The study enrolled 23 cats from 4 to 17 years of age from various breeds or breed mixes diagnosed with nonregenerative anemia associated with CKD.

Varenzin-CA1 is a liquid given by mouth to the cat once daily for up to 28 days. The treatment may be repeated as needed after a minimum seven-day pause. Varenzin-CA1 is available only by prescription from a licensed veterinarian given that professional expertise is required to properly diagnose CKD and nonregenerative anemia in cats. 

Before prescribing the drug, veterinarians should advise cat owners about possible side effects, which include vomiting, increases in systolic blood pressure and thromboembolism (blood clots). The FDA encourages cat owners to work with veterinarians to report adverse events or side effects potentially related to the use of any drug, including Varenzin-CA1. 

The FDA granted conditional approval of Varenzin-CA1 to Elanco US Inc.